Tank



FIG. 1 is a perspective view of a tank showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a right side elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken line showing of a toilet bowl and plumbing fixture holes is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a tank, as shown and described. 